Method
1) Place the sweet potato in a large pot and fill with just enoughwater to cover. Bring to a boil and cook until the potato is tenderand easily pierced with a fork, about 10 minutes. Drain thoroughly,transfer to a mixing bowl and mash well.
2) Stir in the red chilli, scallions, garlic, cumin seeds, cilantro and egg yolk and season with salt and pepper to taste.
3) When the mixture is cool enough, use your hands to form the potato mixture into six slightly flattened cakes, about 6in in diameter, and spray with low-calorie cooking spray. Place a large skillet over medium-high heat and cook the potato cakes, three at a time, for about 5–6 minutes until golden brown on each side, turning once.
4) Make the mayo by mixing all the ingredients together in a small bowl. Serve the sweet potato cakes on a bed of arugula or salad leaves with a dollop of the sweet chili mayo and lime wedges.